Cooling head and electronic apparatus

ABSTRACT

A cooling head includes: a first refrigerant flow channel, provided so as to be in contact with an object to be cooled, configured to flow refrigerant; a second refrigerant flow channel configured to flow the refrigerant; and at least one communication hole, provided between both ends of the object to be cooled in the first refrigerant flow channel in a first flow direction of refrigerant in the first refrigerant flow channel, configured to allow the first refrigerant flow channel and the second refrigerant flow channel to communicate with each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-002853, filed on Jan. 10, 2013, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments discussed herein are related to a cooling head and an electronic apparatus.

BACKGROUND

In the boil cooling method, a main flow channel and a sub-flow channel for a cooling liquid are formed in this order from the side of the cooling surface. A plurality of nozzles that penetrate a partition wall separating the sub-flow channel and the main flow channel and that protrude into the main flow channel are arranged in the flow channel direction of the main flow channel, and tip end parts of the individual nozzles are caused to be in the vicinity of or in contact with the cooling surface. The cooling liquid is caused to circulate to the main flow channel and the sub-flow channel, the cooling surface is cooled with boiling of the cooling liquid flowing through the main flow channel, and the cooling liquid on the sub-flow channel side is supplied from the sub-flow channel side through each of the nozzles so as to exude in the vicinity of the cooling surface.

A related art is disclosed in Japanese Laid-open Patent Publication No. 2007-150216.

SUMMARY

According to one aspect of the embodiments, a cooling head includes: a first refrigerant flow channel, provided so as to be in contact with an object to be cooled, configured to flow refrigerant; a second refrigerant flow channel configured to flow the refrigerant; and at least one communication hole, provided between both ends of the object to be cooled in the first refrigerant flow channel in a first flow direction of refrigerant in the first refrigerant flow channel, configured to allow the first refrigerant flow channel and the second refrigerant flow channel to communicate with each other.

The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a cooling system;

FIG. 2 illustrates an example of a relationship between a cooling head and an electronic device;

FIG. 3 illustrates an example of a communication hole;

FIG. 4 illustrates an example of cooling effect;

FIG. 5 illustrates an example of a top view of a first refrigerant flow channel;

FIG. 6A and FIG. 6B each illustrate an example of a top view of the flow of refrigerant;

FIG. 7 illustrates an example of a top view of a second refrigerant flow channel and a communication hole;

FIG. 8 illustrates an example of a top view of a second refrigerant flow channel and a communication hole;

FIG. 9 illustrates an example of arrangement of a communication hole;

FIG. 10 illustrates an example of an exploded perspective view of a cooling head;

FIG. 11 illustrates an example of a perspective view of a cooling head;

FIG. 12 illustrates an example of a sectional view of the cooling head; and

FIG. 13 illustrates an example of a sectional view of a cooling head.

DESCRIPTION OF EMBODIMENTS

In the boil cooling method, a plurality of nozzles protruding into a main flow channel are arranged in the flow channel direction of the main flow channel, and therefore the nozzles may cause a loss (pressure loss) in the flow of cooling water in the main flow channel.

FIG. 1 illustrates an example of a cooling system. The cooling system 1 illustrated in FIG. 1 may be a system for cooling an electronic device 2. The cooling system 1 includes a pump 4, a radiator 6, a cooling head 30, and pipes 10, 12, 14, and 16. The cooling head 30 may include part of the pipe 10, part or the whole of the pipes 12 and 14, and/or part or the whole of the pipe 16.

The cooling head 30 may be provided for the electronic device 2 as illustrated in FIG. 1. The electronic device 2 may be a heat generating device, element, component, or unit. The electronic device 2 may be, for example, a large-scale integration (LSI). An electronic apparatus 50 may include the cooling head 30 and the electronic device 2. The electronic apparatus 50 may be a computer system such as an enhanced server or a supercomputer.

The pipes 12 and 14 bifurcating from the pipe 10 are coupled to the suction side of the cooling head 30. The pipe 16 is coupled to the discharge side of the cooling head 30. The other end of each of the pipe 10 and the pipe 16 is coupled to the radiator 6. Thus, the pipes 10, 12, 14 and 16 and the radiator 6 define a circulation flow channel. The pipe 10 is provided with the pump 4. The pump 4 sucks refrigerant (for example, cooling water) cooled in the radiator 6 and discharges the refrigerant toward the cooling head 30. The refrigerant discharged from the discharge side of the cooling head 30 (refrigerant that receives the heat of the electronic device 2) is supplied to the radiator 6 and is cooled (radiates heat).

The configuration of the cooling system 1 illustrated in FIG. 1 is merely an example, and various modifications are possible. For example, although, in FIG. 1, refrigerant discharged from one pump 4 is branched into two pipes 12 and 14 and supplied to the cooling head 30, refrigerant may be supplied to the cooling head 30 through two independent pipes using two pumps. For example, the pipe 12 may be provided with a valve. In the cooling system 1 illustrated in FIG. 1, a transition tank or the like for creating a subcool state may not be provided.

FIG. 2 illustrates an example of a relationship between a cooling head and a electronic device. In FIG. 2, arrows P01, P02, P1, P2, and P4 schematically indicate the flow direction of refrigerant. The Z direction indicates the vertical direction, and the top of FIG. 2 may be the top in the vertical direction. FIG. 3 illustrates an example of a communication hole. In FIG. 3, communication holes 40′ that have nozzles and allow a first refrigerant flow channel and a second refrigerant flow channel to communicate with each other are illustrated.

The cooling head 30 illustrated in FIG. 2 includes a first refrigerant flow channel 32, a second refrigerant flow channel 34, and communication holes 40.

The first refrigerant flow channel 32 is in contact with an object 3 to be cooled with a lower member 36 a therebetween. The object 3 to be cooled may be an electronic device 2 or an object that receives heat from an electronic device 2. For example, an object directly in contact with the lower member 36 a may be a heat spreader 3 a of an electronic device 2. Although, in FIG. 2, the first refrigerant flow channel 32 is in contact with the object 3 to be cooled from above, the first refrigerant flow channel 32 may be in contact with the object 3 to be cooled from below, or any other direction. The first refrigerant flow channel 32 may be in contact with the entire surface of the object 3 to be cooled as illustrated in FIG. 2, or may be partially in contact with the object 3 to be cooled.

The first refrigerant flow channel 32 defines a closed cross-section, for example, a pipe except for the positions of the communication holes 40. In FIG. 2, the lower member 36 a that defines the lower side of the first refrigerant flow channel 32, and an intermediate member 36 b that defines the upper side of the first refrigerant flow channel 32 are illustrated. The near side or far side (the near side or far side in a direction perpendicular to the X direction and Z direction) of the first refrigerant flow channel 32 may be defined, for example, by the side wall member 36 f or 36 e illustrated in FIG. 5.

Refrigerant is caused to flow through the first refrigerant flow channel 32. The refrigerant from the pipe 14 is introduced into the first refrigerant flow channel 32 as indicated by arrow P01 of FIG. 2, flows through the first refrigerant flow channel 32 as indicated by arrows P1, exits the first refrigerant flow channel 32 and flows to the downstream side as indicated by arrow P4.

The second refrigerant flow channel 34 is provided so as to be adjacent to the first refrigerant flow channel 32. Although, in FIG. 2, the second refrigerant flow channel 34 is adjacent to the upper side of the first refrigerant flow channel 32, the second refrigerant flow channel 34 may be provided so as to be adjacent to the lower side of the first refrigerant flow channel 32, or may be provided so as to be adjacent to the near side or far side (the near side or far side in a direction perpendicular to the X direction and Z direction) of the first refrigerant flow channel 32. The second refrigerant flow channel 34 may be adjacent to the first refrigerant flow channel 32 in any direction.

The second refrigerant flow channel 34 defines a pipe of a closed cross-section (except for the positions of the communication holes 40). In FIG. 2, the intermediate member 36 b that defines the lower side of the second refrigerant flow channel 34, and a lid member 36 c that defines the upper side of the second refrigerant flow channel 34 are illustrated. The near side or far side (the near side or far side in a direction perpendicular to the X direction and Z direction) of the second refrigerant flow channel 34 may be defined, for example, by the side wall member 36 f or 36 e illustrated in FIG. 7.

The second refrigerant flow channel 34 is preferably blocked at the downstream end in the flow direction of refrigerant in the second refrigerant flow channel 34. In FIG. 2, the second refrigerant flow channel 34 is blocked at the downstream end by a blocking member 36 d. Since the flow of refrigerant in the second refrigerant flow channel 34 is blocked by the blocking member 36 d, the inflow of refrigerant in the second refrigerant flow channel 34 into the first refrigerant flow channel 32 through the communication holes 40 (to be described later) is promoted.

Refrigerant is caused to flow through the second refrigerant flow channel. The refrigerant from the pipe 12 is introduced into the second refrigerant flow channel 34 as indicated by arrow P02 of FIG. 2, flows through the second refrigerant flow channel 34, flows into the first refrigerant flow channel 32 through the communication holes 40 as indicated by arrows P2, exits the first refrigerant flow channel 32 and flows to the downstream side as indicated by arrow P4. In FIG. 2, since the blocking member 36 d is provided, the refrigerant introduced into the second refrigerant flow channel 34 flows into the first refrigerant flow channel 32 through the communication holes 40 unless it flows back, and then, it exits the first refrigerant flow channel 32 and flows to the downstream side. When the blocking member 36 d is not provided, refrigerant that does not flow into the first refrigerant flow channel 32 through the communication holes 40, for example, refrigerant that exits from the downstream opening of the second refrigerant flow channel, may flow to the downstream side independently from the refrigerant in the first refrigerant flow channel 32, or may be merged with the refrigerant in the first refrigerant flow channel 32, may then exit the first refrigerant flow channel 32, and may flow to the downstream side. When the blocking member 36 d is provided, it may be advantageous in terms of the number of components and the cooling efficiency as compared to when the blocking member 36 d is not provided.

The communication holes 40 are provided between both ends of the object 3 to be cooled of the first refrigerant flow channel 32 in the flow direction of refrigerant in the first refrigerant flow channel 32. In FIG. 2, the three communication holes 40 are provided between both ends of the object 3 to be cooled of the first refrigerant flow channel 32 in the flow direction of refrigerant in the first refrigerant flow channel 32. Both ends of the object 3 to be cooled may be both ends of the heat spreader 3 a or may be both ends of a heat generating source, for example, the electronic device 2.

The communication holes 40 do not have nozzles and allow the first refrigerant flow channel 32 and the second refrigerant flow channel 34 to communicate with each other. For example, the communication holes 40 may be not in the form of nozzles protruding into the first refrigerant flow channel 32, for example, in the form of the communication holes 40′ illustrated in FIG. 3 but simple holes formed in a flat surface or a curved surface. Communication holes 40′ having nozzles supply the refrigerant in the second refrigerant flow channel to positions close to the object 3 to be cooled. Therefore, in a cooling system using the boiling of liquid, for example, the system that removes bubbles generated by the heat from an object 3 to be cooled illustrated in FIG. 3, communication holes 40′ having nozzles are provided. The communication holes 40′ having nozzles may cause a loss (pressure loss) in the flow in the first refrigerant flow channel 32 and may cause a decrease in cooling capacity.

When focusing on the refrigerant introduced from the pipe 14 into the first refrigerant flow channel 32, the refrigerant introduced from the pipe 14 into the first refrigerant flow channel 32 receives heat from the object 3 to be cooled (receives heat with the cooling of the object 3 to be cooled) as it flows downstream, and therefore the temperature (refrigerant temperature) increases. Therefore, in the refrigerant introduced from the pipe 14 into the first refrigerant flow channel 32, the temperature on the upstream side of the object 3 to be cooled is lower than the temperature on the downstream side of the object 3 to be cooled, and non-uniform cooling may occur.

The difference in temperature produced between the upstream side and the downstream side of flow is temperature variation in the temperature distribution on the surface of the electronic device. A state in which there is temperature variation is a state in which the effect of heat on the electronic device 2 varies, and is a state in which various distortions caused by heat, for example, the load is large. In order to stably operate the electronic device 2 or a system including the electronic device 2, for example, the electronic apparatus 50 over a long period of time, the load on the electronic device 2 may be preferably small.

For example, since the communication holes 40 are provided between both ends of the object 3 to be cooled in the first refrigerant flow channel 32 in the flow direction of refrigerant in the first refrigerant flow channel 32, non-uniform cooling may be remedied. For example, at a position where the temperature of refrigerant introduced into the first refrigerant flow channel 32 increases, refrigerant in the second refrigerant flow channel 34, for example, fresh refrigerant is introduced through the communication holes 40, and therefore the increased temperature of refrigerant in the first refrigerant flow channel 32 decreases, and the cooling capacity may recover. Since the increase in the temperature of refrigerant on the downstream side of flow is reduced, the cooling capacity of refrigerant may be uniformized along the flow direction. Therefore, the load on the electronic device 2 may be reduced.

The positions and number of the communication holes 40, the flow rate of refrigerant introduced from the second refrigerant flow channel 34 through the communication holes 40 into the first refrigerant flow channel 32, and the like may be set taking into account the heat generation distribution of the object 3 to be cooled, such that the temperature distribution of the object 3 to be cooled along the flow direction is a desired temperature distribution, for example, a uniform temperature distribution.

FIG. 4 illustrates an example of cooling effect. In FIG. 4, in each of the case of uniform heat generation and the case in which there is a hot spot, two types of temperature distribution are illustrated. The uniform heat generation means that the amount of heat generation is uniform in each region of the electronic device 2. The hot spot means a part of the electronic device 2 in which the amount of heat generation is larger than in the other parts due to non-uniform heat generation, for example, a part in which the amount of heat generation is locally the maximum in a state where the electronic device 2 is alone. In FIG. 4, the hot spot H may exist, for example, on the downstream side in the flow direction of refrigerant of the electronic device 2. The temperature distribution illustrated in FIG. 4 is temperature distribution after cooling, and may correspond to the temperature distribution of the electronic device 2 (the temperature distribution on the surface of the electronic device). In each graph illustrating temperature distribution, the horizontal axis indicates temperature measurement position (the origin side corresponds to the upstream side in the flow direction of refrigerant), and the vertical axis indicates temperature. For example, each graph illustrates the temperature distribution along the flow direction of refrigerant.

In FIG. 3, in the case of the uniform heat generation, the temperature distribution is such that, as illustrated in A of FIG. 4, the temperature increases significantly in the center, and increases gradually toward the downstream side. The reason is that the temperature of refrigerant increases on the downstream side. In the case of a hot spot, the temperature distribution is such that, as illustrated in A of FIG. 4, the temperature increases gradually toward the downstream side, and increases steeply near the hot spot. The reason is that the temperature of refrigerant increases steeply owing to the hot spot on the downstream side. As just described, since refrigerant circulates in a direction, under the influence of temperature state of refrigerant, the electronic device 2 may not be cooled uniformly.

In FIG. 2, the object 3 to be cooled is cooled substantially uniformly. Therefore, in the case of uniform heat generation, the temperature distribution is an arcuate temperature distribution as illustrated in B of FIG. 4. Also in the case of a hot spot, the temperature distribution is an arcuate temperature distribution as illustrated in B of FIG. 4, and the temperature increases only slightly near the hot spot. In both cases, the maximum temperature T1 is low as compared to FIG. 3.

FIG. 5 illustrates an example of a top view of a first refrigerant flow channel. The first refrigerant flow channel 32 may be a single flow channel for one object 3 to be cooled, or may include a plurality of flow channels 32 a to 32 h for one object 3 to be cooled as illustrated in FIG. 5. The plurality of flow channels 32 a to 32 h may extend parallel to each other. The plurality of flow channels 32 a to 32 h are divided from each other by partition walls 33 between the side wall members 36 e and 36 f in the Y direction. Although, in FIG. 5, the intervals in the Y direction between the plurality of flow channels 32 a to 32 h are substantially the same, the intervals between some or all of the plurality of flow channels 32 a to 32 h may differ. Although the intervals in the Y direction between the plurality of flow channels 32 a to 32 h are substantially fixed along the X direction, they may change, for example, they may increase downstream. Although, in FIG. 5, the plurality of flow channels 32 a to 32 h exist from end to end in the X direction (flow direction), the partition walls 33 may be formed in only a part of the first refrigerant flow channel 32. The partition walls 33 may be formed over the entire range of the electronic device 2 (or the object 3 to be cooled) in the flow direction, or may be formed only in a range under the communication holes 40. Although, in FIG. 5, all of the plurality of flow channels 32 a to 32 h pass over the same electronic device 2 (or object 3 to be cooled), only some of the plurality of flow channels may pass over the same electronic device 2 (or object 3 to be cooled).

FIG. 6A and FIG. 6B each illustrate an example of a top view of a flow of refrigerant. In FIG. 6A, the flow of refrigerant near a communication hole 40 in the case where the first refrigerant flow channel 32 includes a single flow channel is illustrated. In FIG. 6B, the flow of refrigerant near a communication hole 40 in the case where the first refrigerant flow channel 32 includes a plurality of flow channels 32 a to 32 h is illustrated.

As indicated by dashed arrows of FIG. 6A, in the case where the first refrigerant flow channel 32 includes a single flow channel, when the refrigerant in the second refrigerant flow channel 34 flows through the communication hole 40 into the first refrigerant flow channel 32, the flow direction of the inflowing refrigerant may be disturbed, and vortexes and stagnation may tend to occur.

As indicated by dashed arrows of FIG. 6B, in the case where the first refrigerant flow channel 32 includes a plurality of flow channels 32 a to 32 h, when the refrigerant in the second refrigerant flow channel 34 flows through the communication hole 40 into the first refrigerant flow channel 32, the disturbance of the flow direction of the inflowing refrigerant or the occurrence of vortexes and stagnation due to disturbance may be reduced. Therefore, all of the refrigerant in the second refrigerant flow channel 34 flowing through the communication hole 40 into the first refrigerant flow channel 32 may be able to be caused to flow along the flow direction of the refrigerant in the first refrigerant flow channel 32.

FIG. 7 illustrates an example of a top view of a second refrigerant flow channel and a communication hole. For example, when the configuration illustrated in FIG. 7 and the configuration of the first refrigerant flow channel 32 including a plurality of flow channels 32 a to 32 h illustrated in FIG. 5 are combined, the second refrigerant flow channel 34 may be disposed over the first refrigerant flow channel 32 such that they are completely superimposed on each other in top view. For example, a two-tiered structure may be formed.

Although, in FIG. 7, the second refrigerant flow channel 34 is a single flow channel defined between the side wall members 36 e and 36 f in the Y direction, it may include a plurality of flow channels as with the first refrigerant flow channel 32. The communication holes 40 may be formed, as illustrated in FIG. 7, so as to be elongate in a direction (Y direction) across the flow direction (X direction) of the refrigerant in the first refrigerant flow channel 32. When combined with the configuration of the first refrigerant flow channel 32 including a plurality of flow channels 32 a to 32 h illustrated in FIG. 5, each communication hole 40 may be shared by at least two of the plurality of flow channels 32 a to 32 h. In FIG. 7, in the case of the uniform heat generation, the necessity of cooling the end portions of the object 3 to be cooled may be not so high. Therefore, the communication holes 40 may not communicate with the flow channels 32 a and 32 h at both ends in the Y direction. The communication holes 40 may be formed so as to communicate with all of the flow channels 32 a to 32 h of the first refrigerant flow channel 32.

FIG. 8 illustrates an example of a top view of a second refrigerant flow channel and a communication hole. When the configuration illustrated in FIG. 8 and the configuration of the first refrigerant flow channel 32 including a plurality of flow channels 32 a to 32 h illustrated in FIG. 5 are combined, the second refrigerant flow channel 34 may be disposed over the first refrigerant flow channel 32 such that they are completely superimposed on each other in top view. For example, a two-tiered structure may be formed.

In FIG. 8, the plurality of flow channels 32 a to 32 h are provided with their respective communication holes 40. The example illustrated in FIG. 8 may be combined with the example illustrated in FIG. 7. For example, a plurality of communication holes 40 provided for one electronic device 2 may include communication holes 40 each corresponding to one of the plurality of flow channels 32 a to 32 h, and communication holes 40 each shared by some of the plurality of flow channels 32 a to 32 h.

FIG. 9 illustrates an example of an arrangement of communication hole. In FIG. 9, an example of arrangement of communication holes in the case where there are hot spots on the electronic device 2 is illustrated.

In the case where there are hot spots on the electronic device 2, communication holes 40 may be provided so as to correspond to the positions of the hot spots in the X direction, or may be provided on the upstream side of the positions of the hot spots. Refrigerant having high cooling capacity, for example, the refrigerant in the second refrigerant flow channel 34 is introduced near the hot spots of the electronic device 2. Therefore, the hot spots of the electronic device 2 may be cooled intensively and efficiently. When sufficient pressure for the inflow of the refrigerant in the second refrigerant flow channel 34 through the communication holes 40 into the first refrigerant flow channel 32 is obtained, the communication holes 40 may be provided just above the hot spot H1 so as to correspond to the position of the hot spot H1. When sufficient pressure for the inflow of the refrigerant in the second refrigerant flow channel 34 through the communication holes 40 into the first refrigerant flow channel 32 is not obtained, the communication holes 40 may be provided on the upstream side of the position of the hot spot H1. In FIG. 9, the positions of two hot spots in the X direction are indicated by signs H1 and H2. The communication hole 40 on the upstream side is formed just above the hot spot H1 so as to correspond to the position of the hot spot H1, and the communication hole 40 on the downstream side is formed on the upstream side of (just short of) the position of the hot spot H2.

FIG. 10 illustrates an example of an exploded perspective view of a cooling head. The cooling head 30A illustrated in FIG. 10 may differ from the parts of the cooling head 30 illustrated in FIG. 5 and FIG. 7, for example, in the number of the partition walls 33, and the length of the communication holes 40. In other respects, the configuration illustrated in FIG. 10 may be substantially the same as or similar to the configuration illustrated in FIG. 5 or FIG. 7.

The cooling head 30A includes a first flow channel member 100, a second flow channel member 200, and a lid member 36 c. The first flow channel member 100, the second flow channel member 200, and the lid member 36 c may be formed of a highly heat-conductive material, for example, copper. The first flow channel member 100, the second flow channel member 200, and the lid member 36 c may be integrated by welding or the like.

In the first flow channel member 100, a first refrigerant flow channel 32 is formed. In FIG. 10, as with the example illustrated in FIG. 5, a plurality of partition walls 33 are provided in the first flow channel member 100. Therefore, the first refrigerant flow channel 32 has a plurality of flow channels. The first flow channel member 100 includes a joint portion 102 coupled to the pipe 14 (see FIG. 1) from the pump 4, and a joint portion 104 coupled to the pipe 16 (see FIG. 1) leading to the radiator 6. In FIG. 10, refrigerant introduced through the joint portion 102 flows into the first refrigerant flow channel 32 through an upstream flow channel 106 whose width increases toward the downstream side. In FIG. 10, refrigerant that exits the first refrigerant flow channel 32 and flows to the downstream side flows to the joint portion 104 through a downstream flow channel 108 whose width decreases toward the downstream side.

The second flow channel member 200 is stacked on the first flow channel member 100. In the second flow channel member 200, a second refrigerant flow channel 34 and communication holes 40 are formed. The second flow channel member 200 includes a joint portion 202 coupled to the pipe 12 (see FIG. 1) from the pump 4. The downstream side of the second flow channel member 200 is blocked by a blocking member 36 d, and therefore there may be no joint portion leading to the radiator 6. In FIG. 10, refrigerant introduced through the joint portion 202 flows into the second refrigerant flow channel 34 through an upstream flow channel 206 whose width increases toward the downstream side. In FIG. 10, a downstream flow channel 208 corresponding to the downstream flow channel 108 is formed in the second flow channel member 200. However, the downstream flow channel 208 may not be provided. In this case, the blocking member 36 d is moved to the upstream side. The intermediate member 36 b may extend over the downstream flow channel 108 of the first flow channel member 100 and may function as a lid.

The lid member 36 c may have a shape corresponding to the peripheral wall portion of the second flow channel member 200. The lid member 36 c is placed on the second flow channel member 200 and defines the upper side of the second refrigerant flow channel 34.

FIG. 11 illustrates an example of a perspective view of a cooling head. FIG. 12 illustrates an example of a sectional view of a cooling head. In FIG. 12, a sectional view of the cooling head 30B illustrated in FIG. 11 taken along the longitudinal center line of the second flow channel member 220 is illustrated.

The cooling head 30B illustrated in FIG. 11 and FIG. 12 differs from the cooling head 30A illustrated in FIG. 10 in that a second refrigerant flow channel 34 is formed in a pipe-like second flow channel member 220. For example, in the cooling head 30B illustrated in FIG. 11 and FIG. 12, instead of the second flow channel member 200 illustrated in FIG. 10, a pipe-like second flow channel member 220 is provided. In other respects, the configuration of the first flow channel member 100B of the cooling head 30B may be substantially the same as or similar to the configuration of the first flow channel member 100.

The second flow channel member 220 includes a pipe portion 221 that branches from the joint portion 102 and extends upward, a pipe portion 222 that bends from the pipe portion 221 and extends along the flow direction of refrigerant in the first refrigerant flow channel 32, and two pipe portions 223 and 224 that extend downward from the pipe portion 222. The pipe portion 223 has such a form that its width increases toward its lower end as illustrated in FIG. 11. The end in the flow direction of the pipe portion 222 is closed, and refrigerant introduced into the second flow channel member 220 flows from the pipe portions 223 and 224 through communication holes 40 into the first refrigerant flow channel 32 unless it flows back. The communication holes 40 are provided between both ends of the object 3 to be cooled in the first refrigerant flow channel 32 in the flow direction of refrigerant in the first refrigerant flow channel 32.

The cooling head 30B illustrated in FIG. 11 and FIG. 12 may also provide the same advantageous effect as that of the cooling head 30A illustrated in FIG. 10. The first flow channel member 100 and the second flow channel member 220 may not be stacked vertically like the first flow channel member 100 and the second flow channel member 200 of the cooling head 30A illustrated in FIG. 10. In the cooling head 30B illustrated in FIG. 11 and FIG. 12, the pipe portions 223 and 224 extend vertically, and therefore when flowing through the pipe portions 223 and 224, refrigerant obtains a flow velocity in the direction of gravitational force owing to the gravitational force. Therefore, the flowing of refrigerant in the second refrigerant flow channel 34 through the communication holes 40 into the first refrigerant flow channel 32 is promoted.

For example, although the first refrigerant flow channel 32 and the second refrigerant flow channel 34 have a positional relationship (angular relationship) such that refrigerant flows in the same direction, the first refrigerant flow channel 32 and the second refrigerant flow channel 34 may have a positional relationship (angular relationship) such that refrigerant flows in different directions (directions intersecting each other or opposite each other). For example, in FIG. 2, the second refrigerant flow channel 34 may extend in a direction rotated by an arbitrary angle about the Z axis. For example, the second refrigerant flow channel 34 may be mirror-reversed (in this case, refrigerant flows from right to left of FIG. 2), or may be rotated 90 degrees about the Z axis (in this case, refrigerant flows in a direction perpendicular to the X axis and the Z axis).

Although, in FIG. 2, the first refrigerant flow channel 32 and the second refrigerant flow channel 34 are vertically adjacent to each other with the intermediate member 36 b therebetween, the first refrigerant flow channel 32 and the second refrigerant flow channel 34 may be vertically separated from each other. FIG. 13 illustrates an example of a sectional view of a cooling head. For example, in the cooling head 30C illustrated in FIG. 13, an upper member 360 b of a first refrigerant flow channel 32 and a lower member 362 b of a second refrigerant flow channel 34 are vertically offset from each other, and the upper member 360 b and the lower member 362 b may be coupled by pipe members 364 a extending vertically. The lower ends of the pipe members 364 a may be open without having nozzles in communication holes 40.

Although the cooling head 30, 30A, 30B, or 30C is provided for one electronic device 2, it may be shared by two or more electronic devices 2.

In FIG. 2, the lower member 36 a may be a heat spreader 3 a.

The refrigerant may be cooling water or another fluid such as air.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention. 

What is claimed is:
 1. A cooling head comprising: a first refrigerant flow channel, provided so as to be in contact with an object to be cooled, configured to flow refrigerant; a second refrigerant flow channel configured to flow the refrigerant; and at least one communication hole, provided between both ends of the object to be cooled in the first refrigerant flow channel in a first flow direction of refrigerant in the first refrigerant flow channel, configured to allow the first refrigerant flow channel and the second refrigerant flow channel to communicate with each other.
 2. The cooling head according to claim 1, wherein the first refrigerant flow channel and the second refrigerant flow channel communicates with each other without a nozzle.
 3. The cooling head according to claim 1, wherein a downstream end of the second refrigerant flow channel in a second flow direction of refrigerant in the second refrigerant flow channel is blocked.
 4. The cooling head according to claim 1, wherein the second refrigerant flow channel is provided on the side of the first refrigerant flow channel opposite to the side in contact with the object.
 5. The cooling head according to claim 1, wherein the second refrigerant flow channel includes a plurality of flow channels for the object.
 6. The cooling head according to claim 5, wherein the plurality of flow channels extend parallel to each other.
 7. The cooling head according to claim 5, wherein the at least one communication hole is shared by at least two of the plurality of flow channels.
 8. The cooling head according to claim 7, wherein the at least one communication hole is formed so as to be elongate in a direction across the first flow direction.
 9. The cooling head according to claim 1, wherein the at least one communication hole includes a plurality of communication holes for the object, and the plurality of communication holes are arranged in the first flow direction.
 10. The cooling head according to claim 1, wherein the at least one communication hole is provided so as to correspond to the position of a hot spot having a large amount of heat generation of the object or is provided on an upstream side of the position of the hot spot.
 11. The cooling head according to claim 1, further comprising, a first flow channel member in which the first refrigerant flow channel is formed; and a second flow channel member in which the second refrigerant flow channel is formed so as to form a stacked structure.
 12. The cooling head according to claim 1, wherein the refrigerant in the second refrigerant flow channel is merged with the refrigerant flowing through the first refrigerant flow channel at a communication position with the first refrigerant flow channel and flows to the downstream side.
 13. An electronic apparatus comprising: an electronic device; and a cooling head configured to cool the electronic device, wherein the cooling head includes: a first refrigerant flow channel, provided so as to be in contact with an object to be cooled, configured to flow refrigerant; a second refrigerant flow channel configured to flow the refrigerant; and at least one communication hole, provided between both ends of the object to be cooled in the first refrigerant flow channel in a first flow direction of refrigerant in the first refrigerant flow channel, configured to allow the first refrigerant flow channel and the second refrigerant flow channel to communicate with each other.
 14. The electronic apparatus according to claim 13, wherein a downstream end of the second refrigerant flow channel in a second flow direction of refrigerant in the second refrigerant flow channel is blocked.
 15. The electronic apparatus according to claim 13, wherein the second refrigerant flow channel is provided on the side of the first refrigerant flow channel opposite to the side in contact with the object.
 16. The electronic apparatus according to claim 13, wherein the second refrigerant flow channel includes a plurality of flow channels for the object.
 17. The electronic apparatus according to claim 13, wherein the at least one communication hole includes a plurality of communication holes for the object, and the plurality of communication holes are arranged in the first flow direction.
 18. The electronic apparatus according to claim 13, wherein the at least one communication hole is provided so as to correspond to the position of a hot spot having a large amount of heat generation of the object or is provided on an upstream side of the position of the hot spot.
 19. The electronic apparatus according to claim 13, further comprising, a first flow channel member in which the first refrigerant flow channel is formed; and a second flow channel member in which the second refrigerant flow channel is formed so as to form a stacked structure.
 20. The electronic apparatus according to claim 13, wherein the refrigerant in the second refrigerant flow channel is merged with the refrigerant flowing through the first refrigerant flow channel at a communication position with the first refrigerant flow channel and flows to the downstream side. 